Exploring Clang Modules

Given at try! Swift Tokyo 2018

Transcript

1. Exploring Clang Modules
   Samuel Giddins
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2. @segiddins
   CocoaPods, Bundler, RubyGems
   Mobile Developer Experience @ Square
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3. Exploring Clang Modules – Samuel Giddins @ try! Swift Tokyo 2018 3
   

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4. cool_function.h
   #define AUTHORS_NAME "segiddins"
   extern void printMyName(char *);
   main.c
   #include "cool_function.h"
   int main(int argc, char **argv) {
   printMyName(AUTHORS_NAME);
   }
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5. main.c
   extern void printMyName(char *);
   int main(int argc, char **argv) {
   printMyName("segiddins");
   }
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6. #include "header.h"
   #define MAGIC_NUMBER 42
   ...
   ...
   ...
   #include "header2.h" // also includes header.h
   preprocessed into:
   static int secretNumber = -1;
   static int secretNumber = 42;
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7. // header.h
   #ifndef __HEADER_H
   #define __HEADER_H
   ...
   #endif // #ifndef __HEADER_H
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8. #import "header.h"
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9. Enter Module Maps
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10. Exploring Clang Modules – Samuel Giddins @ try! Swift Tokyo 2018 10
    

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11. UsefulFramework.modulemap / module.modulemap
    framework module UsefulFramework {
    umbrella header "UsefulFramework.h"
    export *
    module * { export * }
    }
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12. UsefulFramework.modulemap
    framework module UsefulFramework {
    umbrella header "UsefulFramework.h"
    export *
    module * { export * }
    }
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13. UsefulFramework.modulemap
    framework module UsefulFramework {
    umbrella header "UsefulFramework.h"
    export *
    module * { export * }
    }
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14. UsefulFramework.modulemap
    framework module UsefulFramework {
    umbrella header "UsefulFramework.h"
    export *
    module * { export * }
    }
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15. UsefulFramework.modulemap
    framework module UsefulFramework {
    umbrella header "UsefulFramework.h"
    export *
    module * { export * }
    }
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16. main.swift
    import UsefulFramework
    main.m
    @import UsefulFramework;
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17. Module Maps, the hard part
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18. Module Maps, the hard part
    Lessons from CocoaPods
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19. • Umbrella Directories
    • Explicit Submodules
    • Private Headers
    • Textual Headers
    • ...
    • Automatic Module Map Discovery
    • Relative Paths
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20. Umbrella Directories
    framework module UsefulFramework {
    umbrella "HeadersDirectory"
    }
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21. Explicit Submodules
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22. Explicit Submodules
    framework module UsefulFramework {
    umbrella header "UsefulFramework.h"
    explicit module ForSubclassEyesOnly {
    header "ComplicatedTextField_subclass.h"
    }
    }
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23. Private Headers
    framework module UsefulFramework {
    umbrella header "UsefulFramework.h"
    private header "PrivateHashMapImpl.h"
    }
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24. Textual Headers
    framework module UsefulFramework {
    umbrella header "UsefulFramework.h"
    textual header "AssertMacros.h"
    }
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25. Requires
    framework module UsefulFramework {
    umbrella header "UsefulFramework.h"
    requires objc_arc, blocks, !altivec
    }
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26. Conflicts
    framework module UsefulFramework {
    umbrella header "UsefulFramework.h"
    conflict PointlessFramework, "we do something more useful than that framework"
    }
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27. Automatic Module Map Discovery
    $ tree include
    include
    !"" baking.h
    !"" cake.h
    !"" cookie.h
    !"" module.modulemap
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28. Relative Paths
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29. Relative Paths
    framework module UsefulFramework {
    header "UsefulFramework.h"
    }
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30. Modules & Swift
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31. But my Swift code doesn't have headers...
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32. But my Swift code doesn't have headers...
    It does
    !
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33. swiftc Understands .swiftmodule Files
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34. The Mixed Framework Process
    1. Compile all .swift files
    2. Generate ModuleName-Swift.h in the (empty) .framework
    3. "Extend" existing module map with .Swift submodule
    4. Compile .m files
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35. Extended Module Maps
    module ModuleName.Swift {
    header "ModuleName-Swift.h"
    requires objc
    }
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36. Same-Module Imports
    Superclass.m
    #import
    Subclass.swift
    // nothing to import!
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37. Same-Module Imports
    swiftc Useful.swift
    -module-name UsefulFramework
    -import-underlying-module
    -emit-module
    -emit-objc-header
    -Xcc -fmodule-map-file="UsefulFramework.modulemap"
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38. Swift Static Libraries in CocoaPods
    All of the changes needed:
    https://github.com/CocoaPods/CocoaPods/pull/6966
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39. Are Modules the Future?
    • Tied to headers
    • Swift module stability
    • Still confusing
    • Better than C
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40. Some Resources
    • Clang Docs
    https://clang.llvm.org/docs/Modules.html
    • Clang Source
    https://github.com/llvm-mirror/clang/blob/master/include/clang/
    Basic/Module.h
    • CocoaPods Source
    https://github.com/CocoaPods/CocoaPods/blob/master/lib/
    cocoapods/generator/module_map.rb
    • Trial & Error
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41. @segiddins
    Mobile Developer Experience @ Square
    Exploring Clang Modules
    41
    

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